Broadly stated, the goal of any energy saving system is to prolong the functional life of a device without degrading or disrupting the device's proper operation. To do this, the lifetime of the device's energy source (i.e., the battery) must be extended. Several energy saving techniques designed to accomplish battery life extension are known. The most widely known techniques involve the "Battery Savers" commonly used in the paging receiver arts. Typical of these battery saving techniques are methods to temporarily inactivate selected circuits during periods of non-activity. In more advanced battery savers, it is also known to reduce the operational speed (i.e., clock rate) of microprocessors and other digital circuits. In this way the discharge rate of the battery is reduced thereby extending the pager's operational life between battery replacement or recharge.
The difficulty in extending the paging battery saving techniques to other applications arise fundamentally from the differences between a paging system and, for example, a two-way communication system. Paging systems operate in non-real time. That is, a message (or data) to be forwarded to page an individual is first recorded (or stored), and later played back (transmitted) when the pager has been awaken from a "sleeping" mode (i.e., the battery saver mode). Thus, a paging system provides essentially time delayed one-way communication in a communication system having only a rare need to effect system operational parameter changes, and a system that need not be concerned with access time, channel loading, or channel resource distribution.
Conversely, access time, channel loading, and channel resource distribution are initial and primarily concerns of two-way communication systems. Additionally, system operational parameter changes, channel grants, emergency calls, variation in talk-group affiliations, and the like must be rapidly effected throughout a two-way communication system to maintain the organization of the subscribers operating within the system, and of the system itself. The real-time nature of communication in a two-way system complicates the process since messages cannot simply be stored until transmission is convenient for the communication system.